During the summer I have an ambitious plan to memorize some Greek words; verbs, nouns, adverbs, etc.

My problem is that I don't want to waste time memorizing exotic words, technical uses, or jargon. Furthermore I don't feel like randomly reading the Liddell-Scott. For those recommending that I simply read Greek, accumulating a vocabulary as I go along, I am already doing that.

But is there a list or book, of say, the most commonly used 200-300? words in Ancient Greek? (I am primarily interested in Epic and Attic.)

This is something I've been waiting to get my hands on. It's 1500 of the most common words, so it's too broad for your study, but I think you could simply use a portion of it. Possibly a selection of nouns, adjectives, verbs, etc. I'd love to have all these memorized at some point, that that'll be a while...

Probably you have noticed that the whole word-list is shown at the end of the book from the on-line reader. So, you don't need to buy it. Write down a couple of words in a piece of paper... ten or eleven (as much as you want) to write them down and learn everyday. You will only need to seek for the English word.